To identify your DOT as a v1 or v2 look at the sun hood on your stroller. If the hood has velcro on the peek-a-boo flap, you have a v1. If your hood has no velcro on the peek-a-boo flap, you have a v2 stroller. Additionally, you can look at the seat fabric on your stroller frame - a v2 stroller will use zippers on the seat fabric to recline the seat.
DOT v3 will have the air-free aerotech wheels and is also sold as a double stroller bundle.